Manually-operatable jib cranes



March 17, v1959 R, T, w|| EY l 2,877,905

MANUALLY-OPERATABLE JIB CRANES- Filed July l2, l1955 l-lllmmmlm imun lNvl-:NroR l 37b 3 RICHARD T. WILEY G (D BY v mw' ',the -craneesuiciently ,free y l erator,may'manuallyswing the boom and its load from .anyeone working angular position to any other`(abou't ;the verticall pivotr axis) without undue physicaly effort.

States 2,877,905 Patented Mar. 17, 195-9 Wheeler & Company, Inc., Philadelphia, Pa., a corporation of Pennsylvania Application July 12, 1955, Serial No. 521,551

v s 1 claim. (ci. 212-63) This invention relates to manually-operatable jib cranes o f those ltypes or classes wherein the jib or boom, with its load, may be swung by hand, about a vertical pivot axis, and is particularly concerned with the prob.- lemv of undesired fdrifting of the boom, especially when loaded, from one angular position to another about the vertical axis, ldue to slight misalignments of the pivot axis fromthe true vertical-the primary purpose of the invention being to provide a simple, effective, reliable and inexpensive solution to that problem, particularly by the provision of anti-drift mechanism which will, through years of operation, retain the important characteristic of imposing just enough resistance to drift as to prevent undesired swingingl of the, loaded boom while yet leaving in 'its operation that the opi The drifting,l as'i's well known in the art, is inconvenient :and wasteful of manpower and time, because, for ex- ;ample,when aload is taken onto the crane boom or jib 4when the latter is at onel angular orientation kor azimuth, :and the operator for instance must go to another location :and perhaps arrange a dolly, a vehicle or othermeans to receive the load, the boom in the meanwhilefhas swung to .some other position, which delays matters; butin addi-` tion 'the tendency' to move to the wrong angular'position makes more difficult thel proper spotting of the load atthel location where it is ultimately moved by theoperator.v It is a further object of the invention to solve the foregoing problems by the'provision, of crane anti-drift mechanism of substantially minimumA required'excessresistance to swinging ofthe crane boom, as by the imposition of a frictional drag lonswinging of the boom; and,

in the preferred embodiment, to provide variably settabl'el means 'for imposing such resistance, so that ythe required7 minimum' necessary imposed drag may be varied with considerable nicety. Such variation may be needed after a long period of use, because 'of 'changes in the normal drag von the crane and/ or because of changes in the exactnessoffsetting 'of the vertical pivot axis, which may loccur asa result ofg'radufal vsettling of floors or foundations,'warping 'of wallso'r rcolumns (where the crane is supportedv at-least invpart thereby)v o'r bending of crane or; supporting elements due to thermal or other'efects, or distortion of elements-by virtue ofgrepeated'; excessive, onrlong-sustained loading of the crane, some of.v these effectsbeng notapparent until after a long period of use fof-thec'rane and its anti-drift mechanism in actual operatio'n-g` t" i v l f, More specifically, the yinvention contemplates theI accomplishment ofthe foregoing by the provision of anti drift mechanism associated with one or more of the -bearingsuponwhich the rcrane or `its jib or boomis mounted tofswinghabouta generally vertical axis. Still'mores'pecically, in a crane having a foot-bearing and a headbearing, wherein ,each takes aradial bearing load-said bearings being generally of one or another so-called fanti-friction?? type, but which are of course subject to friction'whose absolute value varies with loading-the invention contemplates the association with at least one of said bearings of a means for imposing a frictional drag on the swinging operation of the crane boom; and, in the preferred embodiment, a frictional drag on the bearing itself, ysuiicient, in combination with the normal friction of the bearings under the particular condition of load, to prevent undesired drifting, but insucient to prevent intentional manual operation of the crane.

Generally, one of theibearings for the vertical axis of the crane takes vertical. thrust loads as well as radial loads, and most typically it is the foot-bearing which takes-the vertical thrust load, and the inventionl conteml plates the association of the anti-drift mechanism with g beingvrelieved of the thrust loads,

the other radial bearing, which is generally the headbearing. `One advantage of this association arises from the fact that the combined radial and thrust bearing is desirably a rolling type of bearing, for example a ballbearing, whereas the other bearing-normally `the headbearing-may conveniently be made of a sleeveor bushing-type (for example, a bronze bushing)l to which I find itsimpler to apply the variably settable frictional drag` means of the present invention. Further, this bearing, may be more'lightly loaded initially, so that theaddition of the imposed `fric,- tionalrdrag thereon `will notresult in a total loadon the bearing so large as to require a very large or heavy bear-y ing, which'might otherwise be the case. Still further,

there is the advantage that this association places the is lessapt to anti-driftmechanism in a location where it be, tampered with vor accidentally damaged `or-y. misadjust'ed; this location (i. e. lthe head-bearing location)A being also desirable as being less subject to the collection.4

of debris or foreign matter, which if it should get in to the adjustable bearing might `interfere with the required nicety of frictional drag setting.

Additionally, y the invention contemplates improvements in the features of construction and operation of crane anti-drifting mechanism as disclosed in the draw? ings and/or as set forthin the following description, together with such other features as may be incident-to the invention or mayvoccur to those skilled inthe art after consideration of this disclosure. In the accompanying drawings: Y l

Figure l is an elevational view of a crane embodying crane, showing the upper trunnionA or pivot pin thereof,4 a'nd associated therewith (in section) the head-bearingv with the variably-settable` friction resistance device associated therewith, this view being taken on the line r2 2 of Figure 3;

' Figure 3 is a horizontal sectional view through-fthe j taken on theline-3-3 of vFigure 2,. a nd`- in bottom plan view, the bearing and'radjustment head-bearing pin, showing, parts associated therewith; and

.Figure 4 is a view similar toy Figure 2,.l but showing 'they' foot-bearing assembly of the crane.

'For'illustrationv of a typical installation embodyingy the l invention, the drawings disclose ar mast type jib-crane.; adaptable tonumerous other types 1 -of cranes, for example ments of mast or other support, with the jib or boom 1 supportedin other ways, with the jib separatelypivoted, Y v brace than the tensiongtyper shown, or with' a lself-supported. jib (having `no,brace), and/or having various Y i Whilel the invention is y with different types or arrangewith other-,types of jib otherfeatures, the'invention is especially well adapted for ready and advantageous utilization in types of cranes where the boom or jib is a rigid beam fixed solidly to an upright crane post or other vertical axis member, which in turn is pivoted on a substantially vertical axis, as by a head-bearing and a foot-bearing.

In the illustrated embodiment, the jib or boom 5, of ordinary I-beam section, is rigidly secured at 6 to a similar upright member 7 and is further supported therefrom by one or more tension braces 8 (in this case a pair of them-one on each side of the axis member 7). The mast or post 7 is carried by a foot-bearing generally indicated at 9, which rests upon the floor, through the intermediation of a pad or plate 11, and by a head-bearing, generally indicated at 12, which is secured to a wall or other structural member or support, such as the column 13 of a factory buildingthrough the intermediation of a headplate 14, a pair of heavy bracket plates 15 and a backing plate 16.

The construction of the head-bearing assembly is shown in Figures 2 and 3 and of the foot-bearing assembly in Figure 4. Before proceeding to the description of said figures, it should be pointed out that the jib may carry a hook or any other means of supporting and/or lifting a load, and in this case it is supplied with an electric hoist 17 which includes a hook 18 raised and lowered by cable 19, and further includes paired brackets 21, each with two wheels or rollers 22, respective pairs of rollers being adapted to ride on the rails formed by the bottom flange of the jib 5.

The jib may be of considerable length, and the load to be lifted and swung by the crane may be of considerable mass, so that the crane itself may at times be deflected slightly, or, for various other reasons set out earlier in this specification, elements of the crane or of the support may be deflected, distorted, or otherwise misaligned, so that the axis of the pivotal supports for the mast 7 may not be always exactly vertical. Under such conditions, the undesired drifting of the boom, hereinbefore discussed, will frequently occur, and it has proven to be quite a problem in some installations, especiallywhere very heavy masses must be readily swung by one man, acting to manually swing the crane and its load.

The total vertical thrust load, and a relatively minor radial load, is taken by the foot-bearing 9. The details of the assembly, as seen in Figure 4, include a pivot pin 23, secured as by welding in the bottom plate 24 of the mast 7; and a double-row ball-bearing 25, of the combined radial and thrust type, the inner race of which surrounds the pin extension 26 (of smaller diameter than pin 23) and takes the thrust from the shoulder thus formed, and the outer race of which rests upon the shoulder 27 of the bearing block 28 which is bolted to the foot-plate 11. A cover-plate 29, bolted in place, and carrying a seal to exclude dirt and retain lubricant, completes the foot-bearing assembly.

The head-bearing assembly, as seen in Figures 2 and 3, includes a pivot pin 31, of larger diameter than the footbearing pin 23 because the pin 31 takes the heaviest radial loads in shear-this pin being welded or otherwise secured in place on the post 7 by any suitable means including the top-plate 32. This assembly further includes an anti-friction bushing (for example of bronze) shown at 33, the same providing a gap-4in this case a pair of gaps 34, as by being split longitudinally. One portion of the bushing seats against,` and is preferably secured to, the fixed backing block 36, and an opposite portion is similarly associated with a movable block 35, forming part of the variably-settable means for imposing an added frictional drag on the bearing. The 'fixed block 36 is solidly fastened, as by welds 36u-36a, to hanged brackets 33 which are in turn secured by bolts or studs 39 to the head-plate 14. The vertical flanges of the brackets 38 form guideways for the movable block 35, which is secured to, and adjusted relative to the xed block, by means of the` bolts `or studs 41, whichnpass through clear holes in fixed block 36 and are threaded into movable block 35. Bolts 37 pass through slots 37a in flanges 38 and are threaded into movable block 35. Lock washers 37b are provided for the bolts 37. To ensure the holding of a given setting, set-screws or the like 42 may be provided, these being screwed into the block 36 and pinching the shanks of bolts 41. To adjust the position of movable block and thus the drag on pin 31 it is necessary to loosen bolts 37 and set-screws 42 and then turn bolts 41. Rotating bolts 41 in direction to screw them further into the tapped holes in block 35 will draw block 35 toward block 36 and thus increase the drag on pin 31.

While different types of bearings may be used at the head and foot of the mast, and variably-settable friction means may be associated with both the head-bearing and the foot-bearing, the present arrangement has all the advantages set out in detail at the beginning of this specification, and is the preferred embodiment for this and other reasons. Just for example: although the loading of the head-bearing surface may be quite high with a heavy load on the jib, its unit loading in pounds per square inch is relatively low as compared with the unit loading on the anti-friction ball elements of the combined radialand-thrust foot-bearing. To the loading of the headbearing there may thus be added an extra frictional drag which is is capable of a rather fine adjustment in relation to the normal friction thereon, and in relation to the drifting tendency of the jib under load.

Because of the very limited duty cycle of the bearing and the very low rate of actual rotation, and also because of the extremely wide variation in the loads imposed on the jib, and for other reasons, it could hardly be predicted that a device such as that herein disclosed could satisfactorily perform under all the imposed conditions, and with sufficiently uniform results over a long period of time; but a full experimental test has shown that the invention effectively accomplishes the purposes and has the advantages set out hereinbefore and gives every indication that a satisfactory performance may be expected throughout the long life characterizing such a crane.

I claim:

In a manually-operatable jib crane, incorporating an upright axis member, a boom adapted when in use to swing about the axis of said member, and a load-carrying device mounted to travel radially of the crane, along said boom between a position adjacent said axis member and an extreme position adjacent the end of the boom, so that undesired drifting of the boom tends to accompany misalignment of the axis of said member relative to the vertical, which tendency is variable in accordance with variations in load and accentuated when said load-carrying device is adjacent the extreme outer end of the boom, an anti-drift mechanism comprising a foot-bearing located adjacent the bottom end of said upright axis member, said foot-bearing adapted to take the chief vertical thrust loads, and being of a rolling anti-friction type with means sealing the same against loss of lubricant and against ingress of foreign matter, and a head-bearing located adjacent the top end of said upright axis member and constructed as a split-sleeve adapted to take the chief radial loads, said head-bearing comprising a fixed backing member for one half of the split-sleeve and a slidable backing member for the other half, together with adjustment means extending through one of said backing members and threaded into the other, and the bearing face area and coefficient of friction of said split-sleeve head-bearing being such that by adjustment of said threaded means a frictional drag may be imposed on said upright axis member suflicient to prevent such undesired drifting of the boom under conditions of maximum load, when the loadcarrying device is in its extreme outward position on said boom, but without interfering with intentional manual swinging of said boom by an operator handling such load.

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS 329.219 Samuel Oct. 27, 1885 489.635 Hemphill etal Jan. 10, 1893 5 1,284,745 Moore Nov. 12, 1918 6 Lund Dec. 9, 1924 Cain Oct. 31, 1933 Arms Mar. 25, 1934 Hoelscther Dec. 26, 1944 Patrosio May 19. 1953 

